1. Field of the Invention
This invention relates to a plunger piston for a pneumatic spring, such as used with motor vehicles. A pneumatic spring acts between a component to be sprung, in particular the vehicle frame, and a resilient component, in particular the axle support of a motor vehicle. The plunger piston is a hollow body, with a plunger piston end located at a bottom and connected with the resilient component, and at a plunger piston end located at a top is connected with a pneumatic spring bellows, which can be charged with compressed air. The pneumatic spring bellows is connected with the resilient component and rolls off on an exterior of the plunger piston shell during spring movements.
2. Discussion of Related Art
Known pneumatic springs are employed in utility vehicles in particular, but also in machinery in which it is necessary to provide a spring action between two components which move in relation to each other. A spring action can be influenced by air pressure, which can be changed in the pneumatic spring bellows.
A difficulty in connection with known pneumatic springs arises because of structural conditions, or also because of restrictions in the structural space, and the plunger piston to which the lower end of the pneumatic spring bellows is attached, does not rest over its entire surface on the resilient component, for example the axle support. This results in problems regarding the functionally dependable attachment during assembly.
Because a known plunger piston is embodied as a hollow body, it is possible that unfavorable installation conditions tension problems can arise in connection with the contact of the lower, open plunger piston end with the axle support. These occur in particular in the area of the contact surface of the lower end of the plunger piston on the resilient component. As a result, deformations, or even the formation of cracks, or breaks because of shearing, can occur, so that it is no longer dependably assured that the pneumatic spring bellows correctly rolls off the exterior of the plunger piston shell during spring movements. Also, a plunger piston which can be inadvertently deformed cannot assure a sufficient transfer of forces and distribution of forces between the pneumatic spring bellows and the resilient component. Also, a satisfactory cushioning effect of the pneumatic spring is not assured.
For overcoming these difficulties it is known from German Patent References DE 197 20 776 A1 or DE 197 33 281 A1, for example in connection with a pneumatic spring, to directly provide the lower circular open end of the plunger piston facing the resilient component with a circular metal plate. The plate is fixedly connected with the plunger piston by a screw connection. This plate is used to protect the open end of the plunger piston from deformation, in particular in the plane of the plate, and simultaneously contributes to the assurance of the dimensional stability of the entire plunger piston. The plate is also used to provide a fastening option between the plunger piston and the resilient component. The plate has screws for this purpose.
The plate mounted on the plunger piston of the known pneumatic spring forms an assembly part which must be additionally attached to the plunger piston. The expense for manufacturing and materials is also thus increased in an undesired way.